#include <bits/stdc++.h>
using namespace std;
long long f[22][16][16];

int main() {
  f[0][0][0] = 1;
  int n, A, B;
  cin >> n >> A >> B;
  for (int i = 1; i <= n; i++)
    for (int j = 0; j <= A; j++)
      for (int k = 0; k <= B; k++)
        for (int s = 0; s <= j; s++)
          for (int t = 0; t <= k; t++)
            f[i][j][k] += f[i - 1][j-s][k-t];
  long long ans = 0;
  for (int j = 0; j <= A; j++)
    for (int k = 0; k <= B; k++)
      ans += f[n][j][k];
  cout << ans;
  return 0;
}